Final answer:
The excessive movement of a slack adjuster suggests that the brake shoes may need adjustment. It is vital to inspect the entire brake system, as there could also be issues with the push rod, slack adjuster, or air pressure.
Step-by-step explanation:
If a slack adjuster moves more than about one inch where the push rod attaches, there could be a few possible issues. It is important to note that slack adjusters are a component of the braking system in large vehicles like trucks and buses. A movement of more than one inch at the point of push rod attachment typically indicates that there is excessive brake chamber stroke, which can have several causes:
- The slack adjuster may require adjustment or replacement if it cannot correctly maintain the brake adjustments.
- The push rod itself may be bent or damaged, and might need to be replaced.
- Brake shoes and related hardware that have worn out may need adjustment or replacement to ensure the push rod does not have to travel as far to apply the brakes.
- If there is an issue with air pressure in the brake system, it could also cause excessive travel in the slack adjuster, indicating that the air pressure needs to be checked and possibly restored to the correct level.
Therefore, the correct answer is that the brake shoes may need to be adjusted, which is option 3. However, it is also good practice to inspect the entire brake system to rule out other issues.